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Thread: 1986 Honda 250sx cam chain timing/tensioning question

  1. #1
    Join Date
    Feb 2023
    Location
    Deansboro
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    11

    1986 Honda 250sx cam chain timing/tensioning question

    Hey guys, I'm new here and I have a question for you. I put a new head on my 1986 Honda 250sx and timed the cam chain according to the manual. With the T lined up with it's mark and the two notches lined up for the cam sprocket and all that good stuff per the service manual. When I put my chain tensioner back in next it moved my cam sprocket timing marks off just a bit. Looks like maybe a tooth worth off but the manual doesn't mention that happening. I put the valve cover back on and adjusted the valves and I can feel it suck on the intake stroke when I turn it with a ratchet. My question is the timing marks. Is that normal for them to be off after the tensioner is installed or did I do something wrong. I went by the manual but just want to be sure. Thanks for any help

  2. #2
    Join Date
    Jul 2009
    Location
    South Florida
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    6,722
    Your timing chain is probably worn out / stretched . Also always time the cam with a little pressure on the guide , can use your finger threw the tensioner hole . This will insure the timing is correct with tension .
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  3. #3
    Join Date
    Feb 2023
    Location
    Deansboro
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    11
    I bought the machine disassembled so before I get too far into putting it back together I should probably revisit the timing.

  4. #4
    Join Date
    Jul 2019
    Location
    Shelton
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    96
    The tensioner only takes slack out on one side, so as the chain stretches the cam timing moves. If you are unsure consider backing it up 1 tooth to see what it looks like to convince yourself where you had it was right. A stretched chain won't line up perfect, but make sure to push on the guide to take slack out like was said above.

  5. #5
    Join Date
    Feb 2023
    Location
    Deansboro
    --
    11
    Ok so I'm assuming that the manual is written as if I wasn't using a worn/stretched chain and the issue I have wouldn't be an issue if I was using a new chain. So when I timed it without tension on the chain, when I installed the tensioner next with my worn/stretched chain I essentially put it a bit out of time? That actually makes sense because it never crossed my mind that my chain would be worn/stretched. Am I understanding you guys correctly?

  6. #6
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    Not that the manual if off , even if the chain was new you have to put a little pressure on the guide to insure the slack is out to set the timing correctly , having a stretched chain just makes it a little harder to get lined up exactly , which it might not .


    Quote Originally Posted by Heavymand View Post
    Ok so I'm assuming that the manual is written as if I wasn't using a worn/stretched chain and the issue I have wouldn't be an issue if I was using a new chain. So when I timed it without tension on the chain, when I installed the tensioner next with my worn/stretched chain I essentially put it a bit out of time? That actually makes sense because it never crossed my mind that my chain would be worn/stretched. Am I understanding you guys correctly?
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  7. #7
    Join Date
    Feb 2023
    Location
    Deansboro
    --
    11
    Oh... OK I'm pickin up what you're puttin down. Any way I look at it I need to re-time it with a little tension on the chain to get it as close as possible.

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